People with clinical depression worry about transmitting the genes to their children, and with good reason, because it is strongly heritable. But as this cheery article in The Times points out, genes and environment interact.
The serotonin transporter gene, 5HTT, also has two alleles, and is known to be involved in mood. Moffitt and Caspi found that people with one allele were 2.5 times more likely to develop clinical depression than those with the other – but, again, only under particular circumstances. The risk applies only to people who also experience stressful life events such as unemployment, divorce or bereavement. When their environments are happy, their genotypes made no difference.
The ghost of Samuel Johnson whispers:
Yet hope not life from pain or danger free,
Or think the doom of man reversed for thee

